1. Field of the Invention
The present invention relates to isolated polypeptides having pectin acetylesterase activity and isolated nucleic acid sequences encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing and using the polypeptides.
2. Description of the Related Art
Pectins are important structural components of plant cell walls. The main backbone in pectins can be divided into linear homogalacturonan (smooth) regions of up to 200 residues of 1,4-linked .alpha.-D-galacturonic acid (GalUA) and highly branched rhamnogalacturonan (hairy) regions consisting of repeating .alpha.-(1,2)-L-rhamnose-.alpha.-(4)-D-galacturonic acid disaccharide units. In general, about half of the rhamnose residues are substituted with neutral oligosaccharides such as arabinans, galactans, and arabinogalactans. Most pectic substances are also esterified at some of the .alpha.-D-galacturonic acid residues with methyl at the carboxyl group or acetyl at the hydroxyl groups at the C-2 and/or C-3 positions.
Pectin acetylesterase catalyzes the deacetylation of the acetyl groups at the hydroxyl groups of the linear homogalacturonan (smooth) regions. Rhamnogalacturonan acetylesterase catalyzes the deacetylation of the acetyl groups at the hydroxyl groups of the highly branched rhamnogalacturonan (hairy) regions.
Pectin acetylesterases have been isolated from Erwinia chrysanthemi (Shevchik et al., 1997, Molecular Microbiology 24: 1285-1301); Vigna radiata L (Breton et al., 1996, FEBS Letters 388: 139-142); and Aspergillus niger (Searle-Van Leeuwen et al., 1996, Progress in Biotechnology pp. 793-798.
A rhamnogalacturonan acetylesterase has been isolated from Aspergillus aculeatus (Kauppinen et al., 1995, Journal of Biological Chemistry 270: 27172-27178; WO 93/20190).
A gene encoding pectin acetylesterase has been isolated from Erwinia chrysanthemi (Shevchik et al., 1997, supra).
A gene encoding rhamnogalacturonan acetylesterase has been isolated from Aspergillus aculeatus (Kauppinen et al., 1995, supra).
It is an object of the present invention to provide improved polypeptides having pectin acetylesterase activity and nucleic acids encoding the polypeptides.